rejction notice but didn't send it to THAT address

I am sending emails to a friend's current email address which is a comcast email. I am getting a Delivery Notification telling me the email could not be delivered to her OLD hotmail address. I'm not sending it to her old hotmail address. I called her and the email is going thru to her comcast address. This just started 2 days ago. Why am I getting this failur delivery notification?

I thought of the forwarding thing, and checked with her .... She says no because she closed her hotmail account QUITE some time ago and hasn't used it in months/years. This just started happening a few days ago. Thanks for checking this. Below is the reject email and a copy of the attachment (my orig email to her):

This really sounds like either your contact has 2 email addresses associated with them or the comcast account is forwarding at least a copy of the email to their hotmail account. Double check both places again.